Rubber Molding Processes

Rubber molding transforms uncured rubber or elastomers into usable products. In addition to shaping parts, molding involves chemical processes that harden or toughen raw rubber polymer chains.

Molding provides quality, durability, and adaptability to multiple industries.

You need the right manufacturing process to achieve the desired result with a mold. Selecting the right molding procedure for your application ensures optimum performance levels and cost efficiency.

Listed below are four types of rubber molding processes.

1. Compression Molding

Compression molding involves creating preforms of the final product from a rubber compound or mixed raw material. When using preforms, a surplus of material is available for placement inside the cavity, ensuring that the cavity fills quickly.

Molding involves placing uncured rubber into an open mold cavity. Heat and pressure seal the mold cavity, allowing the preform to conform to the mold cavity.

Compression molding is often for low-volume production of medium hardness compounds. The process is mainly for manufacturing rubber O-rings, seals, and gaskets.

Compression molding offers several benefits over other molding processes, including a low cost of tooling and a rapid turnaround time. The process, however, is slower due to the manual handling of the mold and products.

2. Injection Molding

Injection molding refers to a technique used for the molding of plastics. Rubber injection molding, however, successfully alters the plastics process by heating the rubber and exerting considerable pressure on it.

Injection molding begins with efficient material preparation. The process starts by mixing the rubber in bulk, followed by stripping it immediately into continuous strips. The rubber stock strips are then injected into the rubber molding machine.

In the injection unit, as the rubber moves through the channel, it is heated and plasticized to a target temperature. Once the rubber has plasticized, it is injected into a heated mold cavity under high pressure.

As a result of the temperature and pressure, the rubber compound cures. Upon reaching the required degree of cure, the rubber cools and solidifies within the mold.

As a molding process, injection molding is the most efficient. The process is normally suitable for large quantities of small or medium-sized products.

3. Transfer Molding

As with compression molding, transfer molding requires the preparation of raw materials into preforms. However, the preforms do not go in mold cavities but in pots between the top plate and plunger.

Rubber transfer molds include pistons, well pots, sprue plates, cavity plates, and a base plate with a knock-out system to eject finished products.

A heated plunger compresses the material in the pot, which then goes into the cavity through sprues. Until the preform takes the shape of the mold and curing occurs, the plunger stays in place. The hardened, cooled part is then ejected.

Transfer molding is a process for producing solid rubber parts and parts requiring rubber bonding to metal or non-metal surfaces.

4. Melt Molding

Melt molding refers to compression molding with thermoplastic materials. Melt molding involves liquefying the thermoplastic material. The liquid material then goes into the designated mold form.

Polymer resulting from the process cools down and only comes out of the mold when it is fully hardened.

Because melt molding highlights more details, it offers better mechanical properties than compression molding.

Rubber molding offers an infinite number of possibilities. As a result, navigating the industry and all of its offerings can be overwhelming. In different situations, each process has its benefits and limitations. Ultimately, rubber molding is about optimizing time, expenditures, and quality while maintaining the highest efficiency level.